Pneumatic sander



States .i atent @tifice dllhfifi? Patented Feb. 6, 1952 Tex.

Filed Sept. 1, 195b, Ser. No. 53,4% 6 Claims. (El. l-l7tl) This invention relates to surface fishing tools and has reference to a pneumatically powered reciprocating sander.

While pneumatic sanders utilizing a double acting piston to reciprocate a standing block are generally characterized by a smooth and balanced action resulting from equivalence in strokes of opposite directions, the construction of intake and exhaust valve mechanisms presents special difficulties in this type of apparatus and usually results in a valve system which wears at a faster rate than remaining components of the mechanism. Since efficient operation is impeded by deterioration of the valve system in a double acting cylinder, prolongation of the life expectancy of this type of sander presents difficult fabrication problems and entails special skills for effective maintenance. Greatly simplified valve arrangements may be used in a single acting piston which works against spring pressure but such systems, as known heretofore, have been characterized by a lack of balance in the actions of opposite strokes and by percussive forces which lead to excessive vibration and creep in operation of this type of sander. A further disadvantage of reciprocating sanders with single acting pistons is the noise generated by intermittent exhaust during operation of the equipment; this noise masks the sounds of abrasion by which an operator can best determine optimum sanding pressures.

Accordingly, an object of the present invention is to provide a reciprocating sander utilizing a relatively simple yet effective valve mechanism.

Another object of the present invention is to provide a single acting piston capable of driving a reciprocating sander in opposite strokes of equivalent force.

A further object of the invention is to provide a pneumatically powered sander which is quiet in its operation and does not tend to creep.

A particular object of the invention is to provide a single acting pneumatic sander of the reciprocating type wherein speed of its sanding block may be adjusted and the forcesimparted by opposite strokes of the sanding block may be balanced for various pneumatic pressures.

An additional object of the invention is to provide a balanced pneumatic sander which is simple to operate and which has a configuration and hand grip arrangement simulating manual sanding blocks utilized in the automotive paint and body trades so that workmen may readily adapt their previous skills to the use of pneumatic equipment.

These and other objects will become apparent from the following description and the accompanying drawing, wherein:

FIGURE 1 is a side elevational view of the invention.

FIGURE 2 is a partially sectional side elevational view of the invention shown with one-half of the housing removed.

FIGURE 3 is an enlarged side elevational and sectional view of the cylinder, piston, and valve mechanism of the invention,

FIGURE 4 is a front elevational view of the invention.

FIGURE 5 is a sectional view taken along line 5-5 in FIGURE 2.

In the drawing, a housing generally designated by the numeral It is formed in two sections or shells 11 and 12 intersecting along a vertical plane which longitudinally bisects the housing. In the illustrated form of the invention the housing it conforms exteriorly to the shape of manual sanders used in the automotive paint and body trades and includes a grip type rear handle 13 as well as a post 14 comprising an elevated portion of the forward end of the housing. Except in an area immediately beneath the rear handle 13 and a portion of the rear handle, itself, opposed edges of the shells 11 and 12 are contiguous at all points along the plane bisecting the housing it? and the bases of the two shells are flat and coplanar with one another. Within the post 14 laterally opposed bosses 15 are respectively formed in the shells 11 and 12 and an opening 16 in one of the bosses threadedly engages a screw 17 countersunk into and extending through the opposite shell at its boss. Rear bosses 18 likewise project in opposed relationship from opposite shells 11 and 12 into the grip like handle 13 and a screw 19 countersunk into and extending through one of the shells 11 threadedly engages an opening in the boss in the opposite shell 12. A trigger member 2t), cut from flat stock, is positioned within the grip type handle 13 and is pivotally connected at its lower rear end to a pin 21, projecting laterally between and threadedly engaging the shells 11 and 12, and is adapted for pivotal displacement in the plane bisecting the shells. An upper edge 22 of the trigger member 2% projects through a slot 23 in the grip type handle 13 and an aperture 24 is formed in the trigger member about the rear bosses l8 beneath the projecting edges of the trigger member. An arcuate trigger pin 25 comprises the forward portion of the trigger member 20 and extends with clearance forwardly within the grip type handle 13 and thence projects downwardly into the interior of the housing =15 the trigger pin also lies in the plane bisecting the shells 11 and 12. Forward and rear semicircular recesses 26 and 27 are correspondingly formed in the forward and rear walls of each shell 11 and 12 so that horizontally aligned forward and rear circular openings are formed in the housing ll) thereby. A forward bed 28 projects upwardly from the base of each shell 11 and 12 near the forward end thereof and is provided with a concave upper surface formed on a radius from the common axis of the forward and rear circular openings 26 and 27 in the housing it A screw 2? extends laterally through the forward bed 28 of one of the shells 11 and threadedly engages an opening 30 in the forward bed of the other shell 12. A rear bed 31 projects upwardly from the base of each shell 11 and 12 at positions spaced therein from the respective rear walls thereof and the upper surface of each rear bed is likewise concavely formed on a radius from the common axis of the forward and rear circular openings 25 and 27 in the housing ll}. In construction corresponding to that of the forward beds 2%, a screw 32 extends laterally through the rear bed 31 of one of the shells 11 and threadedly engages an opening 33 in the rear bed of the other shell 12. A lateral partition 34 comprised of corresponding members in opposite shells 11 and 12 extends vertically from the rear edge of the rear bed 31 to the grip type opening of the rear handle 13.

A hollow cylinder 35, open at one of its ends, is positioned upon the beds 28 and 31 within the housing 10 and extends forwardly from the lateral partition 34 to a position spaced from the forward wall of the housing. The closed end 36 of the cylinder 35 is nearest the forward wall of the housing 10 and an orifice 37 is formed therein with its center on the common axis of the circular openings 26 and 27 in the forward and rear walls of the housing; the axis of the cylinder also coincides with the common axis of the openings in the forward and rear walls of the housing. A valve seat 38 constructed as a cylindrical nylon tube having a flange 39 radially and outwardly formed from one of its ends is press fit through amass? the orifice 37 with the flanged portion of the valve seat positioned inwardly adjacent the closed end 36 of the cylinder. An outer sleeve 40, also constructed as a cylindrical nylon tube and having its interior diameter corresponding to the exterior diameter of the cylindrical portion of the valve seat 38, is circumjacently press fit over so much of the valve seat as projects outwardly of the cylinder 35, and a flanged portion 41 of the ex-. terior sleeve is positioned exteriorly adjacent the closed end 36 of the cylinde 35. A cylindrical spacer ring 42 having an interior diameter corresponding to the diameter of the flanged portion 41 of the exterior sleeve 40 is positioned between the closed end 36 of the cylinder 35 and the interior surface of the forward wall of the housing where the spacer ring is coaxially disposed with the cylinder and receives the flanged portion of the outer sleeve. The axial length of the spacer ring 42 corresponds to the spacing between the closed end 36 of the cylinder 35 and the forward wall of the housing 10 so that the cylinder extends between the spacer ring and the lateral partition 34 within the housing 10. A plurality of exhaust ports 43 are spaced about and extend radially through the spacer ring 42 and communicate the space within the spacer ring with the remainder of the interior of the housing 10. The circular opening 26 within the forward wall of the housing 10 is provided with threads 44 which receive and engage threads on the exterior surface of a cylindrical plug valve 45 which extends rearwardly through the forward wall of the housing and is provided with a cavity in its rearwardly projecting end and which cavity is adapted for sealing engagement with the outer sleeve 40. Exteriorly of the housing 10 the plug valve 45 is provided with a flange 47 knurled about the periphery 48 of the flange. A cylinder head 49 threadedly engages the rearward end of the cylinder 35 and is provided with a central opening 59 coaxial with the cylinder. A cylindrical piston head 51 smaller in diameter than the interior diameter of the cylinder 35 is positioned therein and is provided with a packer ring 52 attached in sealing engagement to the periphery of the piston head and having a forwardly extending outer portion thereof in sliding and sealing contact with the interior surface or" the cylinder. A tubular piston rod 53 is attached to and extends coaxially and rearwardly from the piston head 51 through the opening 50 in the cylinder head $9 and projects rearwardly and exteriorly of the cylinder 35 through an opening 54 in the lateral partition 34. An arm 55 is perpendicularly attached to the piston rod 53 at the rearward end thereof, and the arm projects downwardly through a longitudinal aperture 56 in the base of the housing It A valve rod 57 extends coaxially through the tubular piston rod 53 and is there slidably supported by a sealed opening 58 in the center of the forward wall of the piston head 51 and by an opening 59 through the rearward end of the piston rod 53 and arm 55; hence, the valve rod is longer than the piston rod and projects exteriorly from the opposite ends thereof. A valve member 69, constructed of nylon or other suitable resilient material and shaped as a semiellipsoid, is secured to a shouldered metal base piece 61 which threadedly engages the forward end of the valve rod 57 so that the major axis of the valve member coincides with the axis of the valve rod. A collar 62 is attached to the valve rod 57 intermediate its ends and is positioned within the tubular piston rod 53 where its outside diameter is slightly less than the interior diameter.

of the piston rod. A valve lifting spring 63 of the helical type is positioned about the valve rod 57 between the collar 62 and the piston head 51 within the tubular piston rod 53. A valve seating spring 64 is correspondingly positioned about the valve rod 57 and within the piston rod 53 between the collar 62 and the piston rod arm 55. A power spring 65, also of the helical type is positioned about the piston rod 53 within the cylinder 35 between the piston head 51 and the cylinder head 49. An air pressure line 66 is connected to a flexible air service line 67 by a swivel nut 68 which threadedly engages one end of an air intake fitting 69 projecting through an opening 70 in the rear of the housing 10. Interiorly of the housing 10 the fitting 67 is threadedly engaged by the air pressure line which also engages a tube 71 communicating the fitting with one side of a button-type quick opening valve 72 positioned within the housing immediately forwardly of the lateral partition 34. The other side of the quick opening valve 72 communicates with a regulator valve 73 having its adjustment handle 74 projecting upwardly through the housing 10 between the grip-type handle 13 and the post 14. The other side of the regulator valve 73 communicates with an air pipe 75 attached to an intake port 76 of the cylinder 35 located in the wall thereof between the piston head 51 and the valve seat 38. The projecting end of the trigger pin 25 is in operating contact with and bears upon the actuating button 77 of the quick opening valve 72.

Rectangular spacer plates 73 and 79, spaced from one another, are positioned adjacently beneath the base of the housing 10 and a bed plate 39 is positioned subjacent the spacer plates where it extends from the forward end of the base of the housing to the longitudinal aperture 56 through which the piston rod arm 55 projects; bolts 81 and 52 extend through the respective spacer plates and bed plate and threadedly engage the base of the housing 10. As best illustrated in FIGURE 4 the width of the bed plate 8% is greater than the width of the spacer plates 78 and '79 so that side edges of the bed plate project laterally beneath and beyond corresponding sides of the spacer plates; bolts 81 and 82 pass through the longitudinal centerlines of the bed plate and spacer plates and the diameters of the heads of the bolts are less than the width of the spacer plates. A channel beam 83, including a horizontal base member 84 and upwardly projecting side members 85 and 86, is provided with inwardly flanged upper edges 87 and 88 of the side members; the lateral width of the bed plate 89 corresponds to the spacing between the side members of the channel beam and the extent of inward projection of the flanges on the upper edges of the side members corresponds to the width of the spacer plates 78 and 79. Therefore, the channel beam 33 is slidably confined to the base of the housing 10 and the bed plate for longitudinal displacement. A lateral spanner 89 is positioned within the channel beam 33 between the side members and 86 thereof and is provided with a central opening which admits and engages the lower end of the piston rod arm 55; screws 99- and 91 extending through the side members of the channel beam threadediy engage opposite ends of the spanner and aflix the position of the same relative to the channel beam. A sanding block 92 is positioned beneath the channel beam 83 in a horizontal disposition and is affixed thereto by screws 93 and 94 extending through countersunk holes in the base of the sanding block and threadedly engaging the base member 84 of the channel beam. At opposite ends of the channel beam 83 clamps 95 and 96 are adapted to engage and hold opposite ends of a strip of sand paper (not shown) extending beneath and adjacent the sanding block 92. The clamps 95 and 96 include longitudinal straps 97 and 98 pivotally mounted for displacement in vertical planes to the base member 84 of the channel beam 83 and outwardly projecting ends 99 and 100 of the straps are formed as obtusely bent pressure plates adapted for engagement with resilient pressure pads 101 and 102 mounted on the sanding block 92 immediately therebeneath. Release handles 103 are positioned at opposite ends and on opposite sides of the channel beam 83 where they extend between and are journaled to side members 85 and 86 of the channel beam. That portion of each release handle 103 extending between side members 85 and S6 of the channel beam 83 is formed as a cam and is positioned immediately beneath the inwardly projecting end of the adjacent strap 97 or 98.

A percussion plate 104 constitutes an innovation of particular importance with respect to construction for balanced operation of the present invention. The rearward end of the valve rod 57 is provided with threads 105 and a rubber disk 106 having a central opening therethrough is positioned about the rearward end of the valve rod. Forward and rear disks 107 and 108 constructed of nylon and corresponding in diameter to the rubber disk 106 are positioned in sandwiched arrangement adjacent opposite faces of the rubber disk to comprise the percussion plate 164, and nuts 109 and 110 engaging the threads 105 on the rearward end of the valve rod 57 are tightened against the respective nylon disks 107 and 108. The circular opening 27 in the rearward wall of the housing is larger in diameter than the nuts 109 and 110 but smaller in diameter than the percussion plate 104.

In operation, pressured air from a tank or compressor (not shown) is conducted through the flexible line 67 and intake fitting 69 and through the air tube 66 to the quick opening valve 72. Depression of the exteriorly projecting edge 22 of the trigger 20 at the grip type handle 13 causes the trigger to pivot on the pivot pin 21 and the trigger pin 25 depresses the actuating button 77 of the quick opening valve 72. Assuming that the regulator valve 74 is appropriately adjusted, pressured air is admitted through the intake port 76 into the cylinder 35 between the forward wall thereof and the piston 51. The power spring 65 expands longitudinally between the cylinder head 49 and the piston head 51 and urges the piston head toward the forward wall of the cylinder; however, forward urging of the piston head by the power spring also urges the rearward end of the piston rod 53 forwardly, and the valve seating spring 64 positioned therein between the collar 62 and the piston rod arm 55 forces the valve 60 into sealing contact with its seat 38. Hence, when the piston head 51 is in its normal position, which is here defined as that position it seeks when working pressure is absent from the cylinder, the power spring 65 and the valve seating spring 64 are each in a state of compression and in mutual equilibrium in that each urges the piston head 51 in an opposite direction. Upon admission of pressured air into the cylinder 35 the flexible ring 52 confines such pressure to the forward portion of the cylinder and the cylinder head 51 is forced rearwardly within the cylinder by compressed air which works against and overcomes the compressive resistance of the power spring 65. As the piston head 51 regresses within the cylinder the tubular piston rod 53 also moves rearwardly and relieves the valve seating spring 64 of its previously described compression; rearward motion of the piston rod relative to the valve rod compresses the valve lifting spring 63 between the collar 62 and the piston head 51. Compression of the valve lifting spring 63 is at first inadequate to unseat the valve 60 because the same air pressure which forces the piston 51 rearwardly within the cylinder 35 tends to hold the valve against its seat 38. The piston rod 53 thus continues its rearward motion until the valve lifting spring 63 has accumulated adequate compressive force to lift the valve 60 from its seat 38 and force the valve rod 57 rearwardly. Once the valve 60 has been lifted from its seat 38 however, an abrupt loss of pneumatic forces tending to keep the valve against its seat permits the valve lifting spring 63 to bear upon the collar 62 and rapidly thrust the valve rod 57 rearwardly with respect to both the cylinder 35 and the piston rod 53; momentum acquired by this abrupt thrust carries the percussion plate 104 into contact with the rearward wall of the housing 10. Assuming the plug valve 45 is open, release of air pressure through the valve seat 38 permits the power spring 65 to expand and drive the piston forwardly within the cylinder 35; such forward motion again compresses the valve seating spring 64 and this compression aided by forward motion of the valve rod 57 acquired through rebounding of the percussion plate 104, once again forces the valve 69 against its seat 38. Forward motion of the piston 51 is limited by complete compression of the valve seating spring 63; rearward motion of the piston is likewise limited by complete compression of the valve lifting spring 64, and motion of the collar 62 on the valve rod 57 is limited by extremes of travel of the valve rod between positions of contact of the valve 60 with its seat 38 and the percussion plate 104 with the rear wall of the housing 10.

An important feature of the present invention is the balancing of forces in opposite directions of motion of the piston within the cylinder. In accordance with Hookes Law and the departures therefrom to be expected under operational conditions, the force required to compress the power spring is substantially inversely proportional to its compressed length; hence, greater forces are required for rearward displacement of the piston as it progresses rearwardly and its motion tends to be forestalled near the rearward limit of its stroke. Likewise, time required for pressure accumulation in the forward portion of the cylinder after the valve 66 has been seated forestalls forward motion of the piston near the forward limit of its stroke and this tendency to dwell is abetted by a decrease in the compressive force during relaxation of the power spring. Seating of the valve 69 during the pistons forward motion is abrupt and this forward percussive force would tend to cause a forward creep in the action of the sander and hamper its manipulation were it not for a counter-percussive force between the percussion plate 11134 and the rearwall of the housing 10 during the rearward motion of the cylinder,

Reciprocation of the piston rod 53 carries the piston rod arm 55 longitudinally backward and forward with respect to the housing 10, and connection of the piston rod arm to the spanner 89 provides a positive and fixed relationship between the piston and the channel beam 83 which is slida-bly attached to the housing 1% by the flanged upper ends 87 and 88 of the side members 99 and 91 of the channel beam between the housing by the bed plate 80.

The mass of the sanding block 5 2 and other reciprocating parts of the sander is small in comparison to the mass of the housing 10 and components attached in fixed relationship thereto; therefore, the inertia of the housing is suflicient to overcome most of the reactive forces resulting from reciprocation of the sanding block.

Power and speed of the sander may be adjusted and maintained by-manipulation of the handle 74 of the regulator valve 73. Since the springs 65, 64 and 63 have fixed values it will be seen that balance in operation of the apparatus would be dependent upon the rate and pressure under which air is admitted into the cylinder 35 unless means for retarding and damping forward motion of the piston rod 53 were also provided. The plug valve 45, by its adjustable contact with or spacing from the outer sleeve 40, controls the exhaust rate of the cylinder 35 and may be used in conjunction with the regulator valve 73 to balance the action of the sander for a variety of operating pressures and speeds. Exhaust gases from the cylinder 35 pass through the exhaust ports 43 in the spacer ring 42 into the interior of the housing 10. By its irregular shape and the presence of interior components which serve as acoustical battles, the housing 10 interiorly performs the function of a mufiier suppressing exhaust noises of the cylinder 35. It should also be noted that there is a rearward flow of exhaust gases about the cylinder 35 within the housing 10; while pressure changes within the cylinder 35 are generally adiabatic, a flow or air about the exterior walls of the cylinder is useful in dissipating frictional heat and maintaining a constant temperature during prolonged use of the sander.

The invention is not limited to the exemplary construction herein shown and described, but may be made in various ways within the scope of the appended claims.

What is claimed is:

1. In a pneumatically powered reciprocating tool, a cylinder including forward and rear ends thereof, an inlet port in a forward wall of said cylinder, means communicating said inlet port with a source of pressured air, valve means interposed in said means communicating said inlet port With said source of pressured air, a piston in said cylinder, a hollow piston rod attached to said piston within said cylinder and extending through said rear end thereof, a helical spring positioned about said piston rod within said cylinder between said piston and said rear end of said cylinder, a valve port including a valve seat in the forward end of said cylinder, a valve adapted to be received in sealing contact with said valve seat in said cylinder, a valve rod attached to said valve and extending through said piston and through said piston rod and projecting rearwardly of said cylinder and said piston rod, a collar secured to said valve rod within said piston rod, a helical valve lifting spring positioned about said valve rod within said piston rod between said piston and said collar, a helical valve seating spring positioned about said valve rod within said piston rod between said collar and the rearward end of said piston rod, and means connecting a reciprocating member to said piston rod.

2. The invention as defined in claim 1 and wherein said valve means communicating said inlet port with a source of pressured air includes a pressure regulator valve and adjustment means for said pressure regulator valve.

3. The invention as defined in claim 2, and including a plug valve positioned exteriorly of the forward end of said cylinder and adapted to adjustably restrict the flow of pressured air through said valve seat.

4. The invention as defined in claim 2, and including a quick opening valve in said means communicating said inlet port with said source of pressured air and a trigger on said quick opening valve in operating connection therewith.

5. A pneumatically operated sander comprising: a holhol housing including a grip type handle, spacer plates attached to the base of said housing, a rectangular bed plate wider than said spacer plates and attached to said spacer plates, a channel beam having inwardly flanged upper edges positioned between said housing and said bed plate laterally of said spacer plates, 21 sanding block secured to said channel beam, a cylinder within said housing and having its longitudinal axis parallel with the length of said bed plate, an inlet port in a first end of said cylinder, means communicating said inlet port with a source of pressured air, a regulator valve positioned within said housing and interposed in said means communicating said inlet port with said source of pressured air, an adjustment handle on said regulator valve and extending exteriorly of said housing, a quick opening valve within said housing and interposed in said means communicating said inlet port with said source of pressured air and having an actuating button, a trigger pivotally mounted within said housing but having a portion of its body projecting exteriorly of said grip type handle, a trigger pin on said trigger and engaging said actuating button of said quick opening valve, a piston within said cylinder, a tubular piston rod attached to said piston and projecting through a second end of said cylinder, a helical spring positioned about said piston rod within said cylinder between said piston and said second end of said cylinder, a valve seat in said first end of said cylinder and communicating the interior of said cylinder with the interior of said housing, a valve adapted to be received in said seat, a valve rod attached to said valve within said cylinder and extending through said piston and through said piston rod and projecting exteriorly of said cylinder and said piston rod, a collar on said valve rod within said piston rod, a valve lifting spring positioned about said valve rod within said piston rod between said piston and said collar, a valve seating spring positioned about said valve rod within said piston rod between said collar and said projecting ends of said piston rod, a percussion plate on the end of said valve rod projecting exteriorly of said cylinder, an interior surface of said housing positioned to be engaged by said percussion plate at one limit of travel of said valve rod, and means connecting said piston rod to said channel beam.

6. The invention as defined in claim 5 and including a sleeve engaging said valve seat exteriorly of said cylinder, a perforated spacer ring coaxially positioned with respect to said sleeve between said first end of said cylinder and the interior wall of said housing, a threaded opening in the wall of said housing in axial alignment with said sleeve and said spacer ring, and a plug valve threadedly engaging said opening in said housing and extending to adjustably obstructing contact with said sleeve.

References Cited in the file of this patent UNITED STATES PATENTS 2,255,395 Spink Sept. 9, 1941 2,499,962 Maul et a1. Mar. 7, 1950 2,681,042 Larson June 15, 1954 2,758,569 Peterson Aug. 14, 1956 

